Generally, a portable drinking receptacle basically consists of a receptacle main body, an inner stopper and a cover serving also as a cup. Both the inner stopper and the cover are fitted on the main body. If one is to drink water directly from the receptacle main body, he or she takes off the cover and the inner stopper and drinks the water with his or her mouth applied to an opening of the receptacle main body. Thus, since the procedures of removing the cover and the inner stopper are troublesome, and since it is inconvenient to take off them when one wants to drink the water in haste during sporting and the like or when one is exercising, water bottles (canteens) having drinking spouts are available so as to cope with uses in such occasions.
Some of such water bottles include those of the structure in which the cap of the bottle is equipped with a drinking spout, and the barrel of the bottle main body is designed to be squeezed and deformed so as to prevent reduction in the internal pressure of the bottle main body from occurring when the water in the bottle is being drunk. Meanwhile, there is another structure, as disclosed in Japanese Utility Model Publication No. Hei 1-27699, in which the water bottle is equipped with a cover having a drinking spout, which can be housed in the cover when the water bottle is not used and which can be pulled out of the cover when the water bottle is used under a pivotal motion of an operating part, and an air vent for preventing reduction in the internal pressure of the bottle main body from occurring, so that the drinking spout may be folded and shut off itself and the air vent when the water bottle is not used.
However, the former water bottle requires a squeezing force for deforming the bottle main body; whereas in the latter water bottle, the structure of folding the drinking spout and that of opening and closing the air vent are complicated.